Horton

Re: Vacuum ERRORs out considering freezing dead tuples from before OldestXmin

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Melanie Plageman <melanieplageman@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>, Andres Freund <andres@anarazel.de>, Noah Misch <noah@leadboat.com>
Date: 2024-06-24T17:33:21Z
Lists: pgsql-hackers

Commits

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  1. Test that vacuum removes tuples older than OldestXmin

  2. Lower minimum maintenance_work_mem to 64kB

  3. Add accidentally omitted test to meson build file

  4. Use DELETE instead of UPDATE to speed up vacuum test

  5. Revert "Test that vacuum removes tuples older than OldestXmin"

  6. Ensure vacuum removes all visibly dead tuples older than OldestXmin

On Mon, Jun 24, 2024 at 1:05 PM Robert Haas <robertmhaas@gmail.com> wrote:
> On Mon, Jun 24, 2024 at 12:43 PM Peter Geoghegan <pg@bowt.ie> wrote:
> > The problem here is that OldestXmin is supposed to be more
> > conservative than vistest, which it almost always is, except in this
> > one edge case. I don't think that plugging that hole changes the basic
> > fact that there is one source of truth about what *needs* to be
> > pruned. There is such a source of truth: OldestXmin.
>
> Well, another approach could be to make it so that OldestXmin actually
> is always more conservative than vistest rather than almost always.

If we did things like that then it would still be necessary to write a
patch like the one Melanie came up with, on the grounds that we'd
really need to be paranoid about having missed some subtlety. We might
as well just rely on the mechanism directly. I just don't think that
it makes much difference.

-- 
Peter Geoghegan